luminosity
n.the amount of light that an object gives off. In astronomy, it helps scientists measure how bright a star is compared to our sun.
n.the total amount of electromagnetic radiation emitted by an astronomical object per unit of time. Often used to describe the intrinsic brightness of a star or galaxy.
“The star has a high luminosity.”
“Astronomers use luminosity to determine the distance to a galaxy by comparing its apparent brightness to its actual output.”
“While the star appears dim to the naked eye, its immense luminosity suggests it is a massive, young object located far beyond our solar system.”
Borrowed from French luminosité or else a native formation from luminous + -ity.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.